Electromagnetic deflection means



April 15, 1958 J. M. N. HANLET 2,831,135

ELECTROMAGNETIC DEFLECTION MEANS Filed June 29, 1954 FIG]: FlgsA FIGA' III III

F I G 8 INVENTOR.

JACQUES MARIE IvoEL l-IANLET H67 WW AT ORN Y United States Patent 2,831,135 ELECTROMAGNETIC DEFLECTION MEANS J 'acques Marie Noel Hanlet, Paris, France, assignor to J. Visseaux S. A., Paris, France The presentinvention relates to an improved method and means for designing an electromagnetic deflecting means for deflecting the cathode ray beam of any cathode ray apparatus intended for such purposes as oscilloscopic, oscillographic, picture analysing or reproducing purposes or the like.

One object of the invention is to, provide an electromagnetic deflecting means of high elficiency with respect to the electrical power supplied thereto for its normal operation.

Another object of the invention is to provide an electromagnetic deflecting means of fairly good deflection properties in that it substantially eliminates such deleterious effects as are apparent in conventional designs as a result of the presence of spurious magnetic fields at both ends of a conventional electromagnetic deflecting means.

Another object of the invention is to provide such an improved electromagnetic deflecting means of high efliciency and good deflection properties that it can be manufactured through a simple and economical method of manufacturing.

In a conventional electromagnetic deflecting coil, each turn of wire, when the coil is developed in a flat form, is of a substantially rectangular configuration; when the coil is shaped for application upon the neck of a cathode ray tube, each turn of wire substantially constitutes a convex quadrilateral. In such wire turn only, the sides which are parallel to the axis on the neck, actually serve for deflection control of the electron beam concerned. Those wire sides which are arcuately bent merely waste part of the power supplied to the coil. Furthermore, the magnetic field generated from said arcuate sides has a deleterious action in that it distorts the useful longitudinal magnetic field and thus causes a variation in the structure of the controlled electron beam at both entrance and exit of the deflecting coil.

In contrast to such a conventional arrangement and in order to avoid such drawbacks, there is provided according to the present invention, an electromagnetic deflecting means wherein each turn of wire when assembled presents a quadrangle having one pair of conductor sides parallel to the generatrices of the deflection space; the other pair of conductor sides being connected to diametrically opposed ends of the first two sides, and when developedin a plane, substantially presents the configuration of a concave quadrilateral having two parallel sides and two diagonal sides, viz. the configuration of a concave oblique parallelogram; after such a winding has been shaped for application upon the neck of a cathode ray tube, two parallel sides of any turn of wire will have their normal efficiency and two. diagonal sides will generate respective magnetic fields resulting when'vectorially combined in a field vector parallel to the longitudinal direction of the field vectors of the two parallel sides thereby eliminating the drawbacks of a conventional electromagnetic deflection means.

According to a further feature of the invention, a method of manufacturing such an improved electromag- "ice netic deflection means is provided which involves the steps of making a flat coil grammatical turns having a diagonal which also represents its height, electrically insulating the flat coil and folding the insulated coil along the diagonal height whereby the two parts of the coil on either side of the diagonal height are superimposed in space the flat form of an electromagnetic deflection winding according to the invention, such form may then be suitably bent at will around the neck or part of the neck of a cathode ray tube so as to represent at least one deflection winding therefor.

These and further features of the invention will be described more fully with reference to the accompanying drawings.

In these drawings:

Fig. 1 represents a conventional electromagnetic deflection means reduced in the interest of clarity, to a single turn of wire each one of the two cooperating windings or coils which together constitute such a deflection means;

Fig. 2 shows the flat developed form of one of these turns of wire;

Fig. 3 represents an electromagnetic deflection means according to the invention also reducing to a single turn of wire each of its two cooperating windings;

Fig. 3A diagrammatically indicates the field distribution in a cross-section of a deflection means according to Fig. 3;

Fig. 4. shows the flat developed form of one of these turns of wire;

Figs. 5, 6 and 7 illustrate different views in the manufacture of a deflection means according to the invention and,

Fig. 8 illustrates the manner whereby in accordance with one feature of the invention a complete electromagnetic deflection means, including two pairs of field Windings for horizontal and vertical deflections of an electron beam, may be obtained from a single manufacturing process.

Fig. 1 shows two. turns of wire ABCD and A B C D on either side of a neck 1 of a cathode ray tube. Each turn is obtained by bending in the suitable arcuate shape a flat rectangular turn such as shown in Fig. 2 at ABCD.

Sides AB and A 13 constitute one dipole element of a pair of dipoles; the other dipole pair is constituted by the opposite sides CD and G l) of the turns of wire.

Each. corresponding pair of turns of wire in an electromagnetic deflection means will similarly define a pair of dipole elements, which are substantially diametrically opposed with respect to neck 1 and which constitute the active portions of the turns, creating an overall deflection magnetic field within this neck the rest direction of which is substantially parallel to the longitudinal axis of this neck.

The arcnate sides AC and ED for one turn of wire, and the arcuate sides A 0 and B D of the corresponding turns of wire, obviously depend in their respective lengths from the. diameter of neck 1. These sections of wire turns are obviously useless for the creation of the useful deflection field within the neck of the cathode ray tube. However they form part of the turns in a proportion which, is the greater, the smaller the axial distance between their planes of disposition with respect to the radius of neck 1. On the other hand, as soon as the electron beam when deflected draws nearer to the edges of the deflection coils, the magnetic field created by these end portions such as BD and E 13 damages the shape of the beam. Such damage is too well known to require further explanations. The damage can bereduced by supporting the coils at some distance from theneck of the tube, but this action increases the length'of such arouate portions and consequently the waste of energy in control power.

or solenoid with convex paralle1o through conductors AB Thus, in each turn of wire of a conventional winding, the useful length AB-I-CD represents too small a portion of overall winding length to enable the complete deflection means to operate with high efi'iciency. From another point of view, the deflection angle for a cathode ray tube, which previously was about 55, frequently reaches now an angle of 70 and even, in certain kinds of cathode ray tubes, is extended to as high as 90. For example, in a deflection means, the length L of a portion of turn such as AB, or CD, may be represented as a function of radius R and half-angle of deflection 6, in the following manner:

( L=R(l+cos )/sin 0 Consequently, the wider the required angle of deflection, the. greater will be the reduction in the useful length L if R is constant. For instance, in an electromagnetic deflecting means so designed as to ensure an angle of deflection equal to 70, the useful length of a turn of wire, AB-i-CD, will be at most equal to 35% of the overall length of this turn of wire. In actual practice this means that a great part of the deflecting power will be lost.

Both these drawbacks, distortion and loss of deflecting power, will be eliminated when, according to the invention, an electromagnetic deflecting means is so made that each of its turns of wire, when developed in a flat form, as shown in Fig. 4, presents the shape of a concave parallelogram. Fig. 3 shows in such a case, the basic arrangement of a pair of deflection coils upon the neck of a cathode ray tube. Fig. 3A illustrates the shape of the magnetic field obtained with such an arrangement, within the neck of the cathode ray tube.

The lateral extension a deflection means can at most be equal to 90. The parallel sides AB and CD, on the one part, A B and GD, on the other part, still play the parts of the active dipole elements for the creation of the useful deflection magnetic field. The direction of the flow of current and CD is the same, and the direction of the flow of the deflecting current through the conductors A B and OD also is the same, but these directions are opposite with respect to each other, and consequently so are the signs of the magnetic fields from the horizontal branches of the first and the second wind ings of the deflection means.

The magnetic field which is created at the intersection of diagonal sides AD and CB of the first coil is the vectorial sum of the magnetic fields due to the flow of deflecting current through these portions of wire. So is the magnetic field created at the intersection of the diagonal sides A D and GB of the second coil. These magnetic fields and their resulting field vector obviously have such a direction that the main component thereof is directed along the axis of the structure in the very direction of the magnetic field created by the above-defined dipole elements. Consequently in an electromagnetic deflection means according to the invention, the part of the power which is taken by the diagonal sides is at least partly recuperated for a useful purpose and the overall efliciency is increased.

.Obviously no deleterious efifect appears at either end of such deflecting structure. components are located in the truly active region of the deflection means, Within its axial extension along the neck of the tube, and no spurious magnetic components are created within this axial space. More specifically, the maximum intensity of the magnetic field resulting from the vectorial combination of the component fields will appear at the mid-plane of this axial space. Such a structure has been found to be of special advantage for a short length deflector having a reduced astigmatismal error.

In the manufacture of such an electromagnetic deflecting means, the following method is used: A fiat solenoid of each of the two coils in such All the useful magnetic or coil 2, Fig. 5, is produced; each of its turns of wire is of a parallelogrammatical shape with diagonal 3 forming the height. The length of this-diagonal in the complete spiral will determine the lateral span or coverage of the deflection means when applied to the neck of the tube.

This spiral parallelogrammatic coil is electrically insulated and then folded along diagonal 3, as shown in Fig. 6. Each one of its turns assumes the configuration shown in Fig. 4. Folding takes place in the flat developed state of the product. After folding, the deflection means may be shaped or arcuated as required for application upon the neck of a cathode ray tube. If necessary, several such products may be superimposed in a pile before being folded and serially connected, or alternatively serially interconnected after individual folding steps. In such a process of manufacture, any number of turns, or any thickness of winding may easily be obtained.

Figs. 5 and 6 show an insulating support 4 which may be either temporary or preserved throughout the manufacture, especially when, according to a preferred embodiment, the manufacture includes the necessary steps for printing the spiral coils.

For instance, as shown in Fig. 7, a thin sheet of insulating flexible material 6, made of polyvinyl on similar plastic material, is provided with a thin sheet or foil 5 of copper or the like. A thermoplastic glue such as a polymerisablerosin, such as known under the trademark Araldite, may be used for holding sheets 5 and 6 together. The thickness of either sheet or foil may be of the order of three to five hundredths of a millimeter.

The face of the metallic foil is cleaned and then coated with a film of a material which, after drying, will be photosensitive and could act as a. photographic layer upon which will be projected a picture of the drawing of the spiral coil. 7

After exposure to light, development and washing, the negative thus obtained is placed in an etching bath so that all parts of the metallic foil uncovered by the resist obtained from the development, are dissolved. This step results in a printed product similar to that shown in Fig. 5. It will suifice to cover the exposed face with an insulating varnish or foil and to fold this composite unit in order toobtain the final product of Fig. 6.

It will ofcourse be of advantage to proceed simultaneously with the manufacture of a plurality of printed deflection coils. As indicated for example in Fig. 8, four spiral solenoids may be placed upon the same insulating backsheet for the manufacture of a complete electromagnetic deflection yoke of a cathode ray tube. Such yoke comprises pairs of windings I and III, and II and IV respectively for horizontal and vertical deflection. Windings I and III will be provided with the same and an adequate number of turns, and so would be windings II and IV. vBefore or after the folding of this composite unit along the diagonal line common to the four spiral coils, the windings I and III will be serially connected over terminals I and III' and similarly the windings II and IV over terminals II and V respectively. The mere application of the printed sheet over 360 around the neck of a cathode ray tube will provide the two-directional electromagnetic deflection means for this tube.

Obviously, any manufacturing process other than printing may be used for putting the invention into practice and to this end any conventional techniques utilising separate insulated wires wound upon parallelogrammatic flat blanks may be used without departing from the scope of this disclosure in this respect.

Having thus described my invention, I claim:

1. In an electromagnetic deflection structure, at least one pair of coils, each of said coils extending in theform of at least one sheeted structure and both of said coils forming a substantially cylindrical deflection space therebetween, each of said coils comprising at least one conductor winding having the general configuration of a quadrangle; one pair of conductor sides being parallel to the generatrices of said deflection space and the other pair of conductor sides connecting diametrically opposed ends of the first two sides; and means for insulating one of the parallel sides and the diainetrical side connected thereto from the other parallel side and the diametrical side connected with said other parallel side and means for insulating said conductor portions.

2. Structure according to claim 1 wherein each coil comprises a plurality of quadrangmlar conductor windings connected in series, and having a common diagonal forming the height of said coil; there being provided one sheeted structure supporting one element of each of said conductor pairs and another sheeted structure superimposed upon said first sheeted structure and supporting the other element of each conductor pair; said conductor windings extending from said first sheeted structure over a separation line formed along said common diagonal into said second sheeted structure superimposed upon said first sheeted structure.

3. Structure according to claim 2 wherein said first and second sheeted structures are formed as a unitary structure attached to each other along said common diagonal.

4. Structure according to claim 2 wherein said common diagonal extends in a plane substantially perpendicular to said deflection space.

5. Structure according to claim 2 wherein said insulating means include insulating sheeting supporting said conductor portions in the form of flat conducting strips.

6. In an electromagnetic one pair of spiral coils of arcuate sheeted configuration oppositely arranged to define a substantially cylindrical deflection space, the windings of each coil having the general shape of quadrangles with two conductor sides being straight and extending parallel to said deflection space, and two other conductor sides being arcuate and connecting diametrically opposite ends of the first two sides; one of said straight sides and the arcuate side condeflection structure, at least 6 nected thereto being insulated from the other straight side and the arcuate side connected to that other straight side, and means for connecting said coils in series.

7. Structure according to claim 6 wherein each coil is arcuated along a portion of a cylindrical surface covering not more than degrees transversely to the direction of said deflection space.

8. Structure according to claim 6 wherein said windings are supported on a common insulated sheeting and provided with an insulating coating.

9. Structure according to claim 6 wherein each of said spiral coils extends over two superimposed sheets forming said sheeted configuration attached to each other along one of the diagonals of said quadrangles.

10. Structure according to claim 6 wherein each of said spiral coils extends over two superimposed sheets forming said sheeted configuration and attached to each other along one of the diagonals of said quadrangle, said diagonal forming the height of said coils and being arranged in a common plane substantially perpendicular to said deflection space.

References Cited in the file of this patent UNITED STATES PATENTS Tech and Electronics Industries, December 1954, pp. 82, 83, and 141.

Brunetti et al.: Printed Circuit Techniques, National Bureau of Standards Circular 468, November 15, 1947,

pp. 17 and 18. 

